Despite a 30-year lifespan that provides ample time for cells to grow cancerous, a small rodent species called the naked mole rat has never been found with tumors of any kind—and now biologists at the University of Rochester, and colleagues, think they know why. The researchers’ findings showed that the mole rat's cells express a gene called p16 that makes the cells "claustrophobic," stopping the cells' proliferation when too many of them crowd together, cutting off runaway growth before it can start. The effect of p16 is so pronounced that when researchers mutated the cells to induce a tumor, the cells' growth barely changed, whereas regular mouse cells became fully cancerous. "We think we've found the reason these mole rats don't get cancer, and it's a bit of a surprise," said Dr. Vera Gorbunova, the senior author of the study. "It's very early to speculate about the implications, but if the effect of p16 can be simulated in humans we might have a way to halt cancer before it starts." The results were reported online on October 26 in PNAS. [Press release] [PNAS abstract]